This invention relates generally to microwave, electromagnetic radiation and more particularly to a method and apparatus for producing controlled, coherent microwave radiation from a warm, uniform plasma at approximately twice the plasma frequency.
Previously, experimental evidence and research had indicated that warm, uniform plasma was capable of incoherent radiated power caused by scattering of plasma waves by density fluctuations. Further, when longitudinal electrostatic waves are excited in the plasma, the attendant scattering, known as Rayleigh scattering, consists of two components (a) a strong longitudinal electrostatic component which remains in the plasma volume and (b) a comparatively weak, transverse, electromagnetic component, a part or all of which radiates out of the plasma. Also noted has been the phenomenon known as Raman scattered waves, which are transverse, electromagnetic; however, they are much weaker than the transverse Rayleigh scattered component. We have discovered the means for controlling Raman scattered components by intensifying the energy density of the Rayleigh scattered longitudinal wave above a certain threshold value. The Raman scattering under these conditions becomes stimulated rather than spontaneous and is amplified coherently to yield intense radiation from the plasma. This process although vaguely similar, is not an exact analogy to the quantum stimulated Raman emission process.